Motor driving apparatus for controlling plurality of motors with less motor driving units than motors

ABSTRACT

The motor driving apparatus comprises a plurality of motors for displacing the position of the control object member, semiconductor switch pairs, a plurality of motor driving units for connecting the motors to the power supply and a control unit for ON/OFF controlling the semiconductor switch pairs. The motors form two sets of motors with each set being formed of two motors. One end of the motors and forming each set is connected to the common motor driving unit having the semiconductor switch pair and the other end of the motors and forming each set is connected to the motor driving units having the semiconductor switch pairs in each set. When the motors of each set are driven simultaneously, the control unit turns ON and OFF two semiconductor switch pairs and drives the motors of each set on the time division basis to provide inverse output polarities of the two semiconductor switch pairs connected to the motors of each set. Thereby there is provided a low price motor driving apparatus that has reduced the total number of motor driving units using the motor driving units having the semiconductor switch pairs.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor driving apparatus andparticularly to a motor driving apparatus for controlling a plurality ofmotors to displace the position of the control object member with lessmotor driving units including a pair of semiconductor switches than themotors.

2. Description of the Related Art

In general, a vehicle uses a plurality of motors to displace theposition of the control objects member such as power seats and powermirrors or the like and the motor driving units of the same number asthe motors are used to individually drive these motors. Moreover, amotor driving apparatus is composed of a plurality of motors, aplurality of motor driving units and a control unit. In this case, it ispreferable that the motor driving apparatus is as low in price aspossible because the motor driving units in the same number as themotors used must be provided. Therefore, a motor driving unit comprisinga pair of relays has been used.

Here, FIG. 5 is a circuit diagram illustrating an example of theessential structure of the known motor driving apparatus. This structureutilizes a motor driving unit including a pair of relays.

As illustrated in FIG. 5, the known motor driving apparatus is composedof a first motor 41 ₁, a second motor 41 ₂, a third motor 41 ₃, a fourthmotor 41 ₄, a first motor driving unit 42 ₁, a second motor driving unit42 ₂, a third motor driving unit 42 ₃, a fourth motor driving unit 42 ₄,and a control unit 43. In this case, the first motor driving unit 42 ₁includes two relays 44 ₁, 44 ₂, the second motor driving unit 42 ₂includes two relays 45 ₁, 45 ₂, the third motor driving unit 42 ₃includes two relays 46 ₁, 46 ₂ and the fourth motor driving unit 42 ₄includes two relays 47 ₁, 47 ₂.

The first motor driving unit 42 ₁ is connected at one end of coils (notdesignated with the reference numeral) of the relays 44 ₁, 44 ₂ to a DCpower supply and to a control unit 43 at the other end. The movablecontacts (not defined with the reference numerals) of the relays 44 ₁,44 ₂ are respectively connected to one end and the other end of thefirst motor 41 ₁. One fixed contacts (not defined with the referencenumerals) of the relays 44 ₁, 44 ₂ are connected to the DC power supply,while the other contacts thereof (not defined with the referencenumerals) are grounded. The second motor driving unit 42 ₂ is connectedto the DC power supply at one end of the coils (not defined with thereference numerals) of relays 45 ₁, 45 ₂ and to the control unit 43 atthe other end. The movable contacts (not defined with the referencenumerals) of the relays 45 ₁, 45 ₂ are respectively connected to one endand the other end of the second motor 41 ₂ respectively. The one fixedcontacts (not defined with the reference numerals) of the relays 45 ₁,45 ₂ are connected to the DC power supply, while the other fixedcontacts (not defined with the reference numerals) are grounded. Thethird motor driving unit 42 ₃ is connected to the DC power supply at oneend of coils (not defined with the reference numerals) of the relays 46₁, 46 ₂, while to the control unit 43 at the other end. The movablecontacts (not defined with the reference numerals) of the relays 46 ₁,46 ₂ are respectively connected to the one and the other ends of thethird motor 41 ₃. The one fixed contacts (not defined with the referencenumerals) of the relays 46 ₁, 46 ₂ are connected to the DC power supply,while the other fixed contacts (not defined with the reference numerals)are grounded. The fourth motor driving unit 42 ₄ is connected to the DCpower supply at one end of the coils (not defined with the referencenumerals) of the relays 47 ₁, 47 ₂, while to the control unit 43 at theother end. The movable contacts (not defined with the referencenumerals) of the relays 47 ₁, 47 ₂ are respectively connected to the oneend and the other end of the second motor 41 ₄. The one fixed contacts(not defined with the reference numerals) of the relays 47 ₁, 47 ₂ areconnected to the DC power supply, while the other fixed contacts (notdefined with the reference numerals) are grounded.

This known motor driving apparatus operates as follows.

First, when the control voltage for the grounded voltage is supplied tothe coil of relay 44 ₁ of the first motor driving unit 42 ₁ from thecontrol unit 43, the coil is energized to switch the movable contactthereof to the condition illustrated in the figure and thereby the powersupply voltage is supplied through the contract switched to one end ofthe first motor 41 ₁. Simultaneously, when the control voltage of thepower supply voltage is supplied to the coil of relay 44 ₂ of the firstmotor driving unit 42 ₁ from the control unit 43, the coil is notenergized to keep the movable contact thereof in the conditionillustrated in the figure and thereby the ground potential is suppliedthrough the contact held at the other end of the first motor 41 ₁.Therefore, a drive current flows to the other end from one end in thefirst motor 41 ₁ and this first motor 41 ₁ rotates in one direction.Thereafter, when the polarity of the control voltage supplied to thefirst motor driving unit 42 ₁ from the control unit 43 is inverted, themovable contacts of the relays 44 ₁, 44 ₂ are set to the invertedcondition of the condition illustrated in the figure and the polarity ofthe voltage supplied to one end and the other end of the first motor 41₁ is also inverted, a drive current flows to one end from the other endin the first motor 41 ₁ and thereby the first motor 41 ₁ rotates in theother direction.

Moreover, when the control voltage same as that supplied to the firstmotor driving unit 42 ₁ from the control unit 43 is supplied to thesecond motor driving unit 42 ₂, third motor driving unit 42 ₃ and fourthmotor driving unit 42 ₄ even in the second motor driving unit 42 ₂,third motor driving unit 42 ₃, fourth motor driving unit 42 ₄, thesecond motor 41 ₂, third motor 41 ₃ and fourth motor 41 ₄ canrespectively be rotated as in the case of rotating the first motor 41 ₁.When the two motors, for example, the first motor 41 ₁ and second motor41 ₂ are rotated simultaneously in the same direction, the movablecontacts of the relays 44 ₁, 44 ₂ of the first motor driving unit 42 ₁and the movable contacts of the corresponding relays 45 ₁, 45 ₂ of thesecond motor driving unit 42 ₂ are switched in the same manner bysupplying the control voltages of the same polarity to the first motordriving unit 42 ₁ and second motor driving unit 42 ₂ from the controlunit 43 and, as a result, the first motor 41 ₁ and second motor 41 ₂ arerotated simultaneously in the same direction. Moreover, when the othertwo motors other than the first motor 41 ₁ and second motor 41 ₂, forexample, the third motor 41 ₃ and fourth motor 41 ₄ are simultaneouslyrotated in the same direction, the same process as that explained aboveis executed.

The known motor driving apparatus explained above uses the motor drivingunits 42 ₁ to 42 ₄ including two relays of the same number as that of aplurality of motors 41 ₁ to 41 ₄ in order to respectively drive aplurality of motors 41 ₁ to 41 ₄. Therefore this apparatus has a meritthat the whole motor driving unit can be formed at a low cost in spiteof use of a plurality of motor driving units 42 ₁ to 42 ₄, but, on theother hand, has a disadvantage that since relays require a comparativelylarge volume, it is difficult to reduce the size of structure of themotor driving apparatus and moreover switching of contacts duringoperation of relays is rather noisy.

Therefore, it is also considered to use the motor driving units 42 ₁ to42 ₄ including a semiconductor switch pair, for example, the fieldeffect transistor pair in place of the motor driving units 42 ₁ to 42 ₄including two relays as a plurality of motor driving units 42 ₁ to 42 ₄.In this case, it is easy to reduce the size of structure of the motordriving apparatus by utilizing the motor driving units 42 ₁ to 42 ₄including the semiconductor switch pair, but the field effect transistorpair that may be used for the motor driving units 42 ₁ to 42 ₄ of aplurality of motors to displace the position of the control objectmember is more expensive than the relays and thereby the manufacturingcost of the motor driving apparatus inevitably becomes higher dependingon the price of the relays.

On the other hand, when the known motor driving apparatus simultaneouslydrives two motors, for example, the motors 41 ₁, 41 ₂, if the drivingtimes of the two motors 41 ₁, 41 ₂ are identical, since the load fordisplacing two members as the control object that are respectivelycoupled with the motors 41 ₁, 41 ₂ does not become identical, thedisplacement amounts of two members as the control object do not becomeuniform and therefore it has been impossible to displace the two membersas the control object under the condition that these members arebalanced.

OBJECT AND SUMMARY OF THE INVENTION

The present invention has been proposed considering the technicalbackground as explained above and the first object of the presentinvention is to provide a motor driving apparatus using a motor drivingunit including small size semiconductor switch pairs in order to attaina totally low price motor driving unit by reducing the total number ofmotor driving units.

Moreover, the second object of the present invention is to provide amotor driving apparatus that can adjust the driving times of two motorsto provide uniform displacement amount of positions of the memberscontrolled with two motors on the occasion of simultaneously driving twomotors to displace the positions of the members as the control object.

In view of attaining the first object explained above, the motor drivingapparatus of the present invention comprises a first structure,including a plurality of motors for displaying the position of a controlobject member during rotation, a plurality of motor driving units havingone or more semiconductor switch pairs to selectively connect aplurality of the motors to the power supply and a control unit forON/OFF controlling the semiconductor switch pairs of a plurality ofmotor driving units, wherein a plurality of the motors form at least aset of motors that is formed with two motors, one end of the motorsforming a set is connected to a common motor driving unit having onesemiconductor switch pair and the other end thereof is connectedrespectively to a motor driving unit having two semiconductor switchpairs, and the control unit drives, when the two motors forming a setare driven simultaneously, two motors on the time division basis byON/OFF controlling the two semiconductor switch pairs to provide inverseoutput voltage polarities of two semiconductor switch pairs of the motordriving unit connected to the two motors.

According to the first structure explained above, a set of motors isformed with two motors among a plurality of motors and one end of twomotors forming a set is connected to the motor driving unit that iscommon to a plurality of motors having a semiconductor switch pair,while the other end thereof is connected to the same motor driving unithaving two semiconductor switch pairs to drive, on the time divisionbasis, two motors via the two semiconductor switch pairs of the samemotor driving unit. Therefore, the total number of motor driving unitsrequired can be reduced in comparison with the total number of motorsused and thereby the total size of the motor driving unit can be reducedto realize a low price motor driving unit.

Moreover, in view of attaining the first and second objects explainedabove, the motor driving apparatus of the present invention comprises asecond structure, including a plurality of motors for displacing theposition of the control object member during rotation, a plurality ofmotor driving units having one or more semiconductor switch pairs toselectively connect a plurality of the motors to the power supply, acontrol unit for ON/OFF controlling the semiconductor switch pair and adisplacement amount detecting unit for detecting the positiondisplacement amount of the control object member, wherein a plurality ofsaid motors form at least a set of motors that is formed of two motors,one end of the motors forming a set is connected to a common motordriving unit including one semiconductor switch pair and the other endthereof is respectively connected to a motor driving unit respectivelyhaving two semiconductor switch pairs and the control unit drives, whenthe two motors forming a set are driven simultaneously, the two motorson the time division basis by ON/OFF controlling the two semiconductorswitch pairs to provide inverted output voltage polarities of the twosemiconductor switch pairs of the motor driving unit connected to thetwo motors and also adjusts each drive time of two motors to provide anequal position displacement amount of the control object members withtwo motors detected by the displacement mount detecting unit in regardto the drive time of two motors.

According to the second structure explained above, the function that issame as that attained with the first structure can be attained and sinceeach drive time of these two motors forming a set is adjusted to makeequal the position displacement amount of the control object member withtwo motors forming a set, the position displacement amount of thecontrol object member with two motors driven simultaneously is alwayskept equal and thereby unbalance condition when the position of thecontrol object member is displaced can be eliminated.

The semiconductor switch pair in the first and second structures issuitably a field effect transistor pair connected in series across thepower supply.

With the structure explained above, the semiconductor switch pair can beformed with a small-size integrated circuit that easily enables mountingof the motor driving unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram illustrating a structure of the essentialportion as the first embodiment of the motor driving unit of the presentinvention.

FIGS. 2(a) and 2(b) are a flowchart of the operation process when twomotors forming a set are driven simultaneously in the motor drivingapparatus as the first embodiment and an explanatory diagram of anexample of the flowing condition of the drive current of two motorsforming a set.

FIG. 3 is a circuit diagram illustrating a structure of the essentialportion of the second embodiment of the motor driving apparatus of thepresent invention.

FIG. 4 is a flowchart of the operation process when two motors forming aset are driven simultaneously in the motor driving apparatus of thesecond embodiment.

FIG. 5 is a circuit diagram illustrating an example of a structure ofthe essential portion of the known motor driving apparatus using a motordriving unit including a pair of relays.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be explainedwith reference to the accompanying drawings.

FIG. 1 is a circuit diagram illustrating a structure of the essentialportion as the first embodiment of the motor driving apparatus of thepresent invention.

As illustrated in FIG. 1, the motor driving apparatus of the firstembodiment is composed of a first motor 1 ₁, a second motor 1 ₂, a thirdmotor 1 ₃, a fourth motor 1 ₄, a first motor driving unit 2 ₁, a secondmotor driving unit 2 ₂, a third motor driving unit 2 ₃ and a controlunit (CPU) 3. In this case, the first motor driving unit 2 ₁ comprises afirst field effect transistor (hereinafter, referred to as FET) switchpair (semiconductor switch pair) 4 and a second FET switch pair(semiconductor switch pair) 5, while the second motor driving unit 2 ₂comprises a first FET switch pair (semiconductor switch pair) 6 and asecond FET switch pair (semiconductor switch pair) 7 and the third motordriving unit 2 ₃ comprises one FET switch pair (semiconductor switchpair) 8. Moreover, in the first motor driving unit 2 ₁, the first FETswitch pair 4 is composed of two FET switches 4 ₁, 4 ₂ connected inseries between the power supply terminal and the ground, while thesecond FET switch pair 5 is composed of two FET switches 5 ₁, 5 ₂connected in series between the power supply terminal and the ground. Inthe second motor driving unit 2 ₂, the first FET switch pair 6 iscomposed of two FETs 6 ₁, 6 ₂ connected in series between the powersupply terminal and the ground and the second FET switch pair 7 iscomposed of two FETs 7 ₁, 7 ₂ connected in series between the powersupply terminal and the ground. In the third motor driving unit 2 ₃, theFET switch pair 8 is composed of two FETs 8 ₁, 8 ₂ connected in seriesbetween the power supply terminal and the ground.

In the first motor driving unit 2 ₁, the first FET switch pair 4 isconnected to the control unit 3 at each gate of FET4 ₁ and FET4 ₂ andalso connected to one end of the first motor 1 ₁ at the connecting pointof FET4 ₁ and FET4 ₂. The second FET switch pair 5 is connected to thecontrol unit 3 at each gate of FET5 ₁ and FET5 ₂ and is also connectedto one end of the second motor 1 ₂ at the connecting point of FET5 ₁ andFET5 ₂. Moreover, in the second motor driving unit 2 ₂, the first FETswitch pair 6 is connected to the control unit 3 at each gate of FET6 ₁and FET6 ₂ and is also connected to one end of the third motor 1 ₃at theconnecting point of FET6 ₁ and FET6 ₂. The second FET switch pair 7 isconnected to the control unit 3 at each gate of FET7 ₁ and FET7 ₂ and isalso connected to one end of the fourth motor 1 ₄ at the connectingpoint of FET7 ₁ and FET7 ₂. Moreover, in the third motor driving unit 2₃, the FET switch pair 8 is connected to the control unit 3 at each gateof FET8 ₁ and FET8 ₂ and is also connected in common to the other end ofthe first to fourth motors 1 ₁ to 1 ₄ at the connecting point of FET8 ₁and FET8 ₂.

In this case, the first motor 1 ₁ and second motor 1 ₂ among the firstmotor 1 ₁, second motor 1 ₂, third motor 1 ₃ and fourth motor 1 ₄ formthe same set, while the third motor 1 ₃ and fourth motor 1 ₄ form thesame set.

Next, FIG. 2(a) is a flowchart illustrating the operation process whentwo motors of the same set, for example, the first motor 1 ₁ and secondmotor 1 ₂ are driven simultaneously in the motor driving apparatus ofthe first embodiment, while FIG. 2(b) is an explanatory diagram of anexample of the drive current waveforms of two motors of the same set.

Operations of the motor driving apparatus of the first embodiment willbe explained with reference to the flowchart of FIG. 2(a) and anexplanatory diagram of FIG. 2(b).

First, in the step S1, the control unit 3 supplies the ground potentialto the gates of FETs 4 ₁, 4 ₂ of the FET switch pair 4 of the firstmotor driving unit 2 ₁ as the control voltages, supplies the powersupply voltage to the gate of FETs 5 ₁, 5 ₂ of the FET switch pair 5 andsupplies the power supply voltage to the gates of FETs 8 ₁, 8 ₂ of theFET switch pair 8 of the third motor driving unit 2 ₃. With supply ofthese control voltages, FET4 ₁, 5 ₂, 8 ₂ turn ON, while FETs 4 ₂, 5 ₁, 8₁ turn OFF. In this case, the first motor 1 ₁ rotates in one directionto displace the position of the control object member coupled with thefirst motor 1 ₁ because the power supply voltage is supplied to one endthereof via FET4 ₁ and the ground potential to the other end via FET8 ₂and thereby a drive current flows as indicated with the time t0 to t1 ofthe upper current waveform of FIG. 2(b). Moreover, in the second motor 1₂, the ground potential is supplied to one end via FET5 ₂, while theground potential to the other end via FET8 ₂ and therefore a drivecurrent does not flow as indicated with the time t0 to t1 of the lowercurrent waveform of FIG. 2(b).

Next, in the step S2, after elapse of a constant period from start ofthe step S1, the control unit 3 switches the supply of the power supplyvoltage to the gates of FETs 4 ₁, 4 ₂ of the FET switch pair 4 as thecontrol voltages and also supplies the power supply voltage as the othercontrol voltage. With supply of these control voltages, FET4 ₂ turns ONtogether with FETs 5 ₂, 8 ₂, FET4 ₁ turns OFF together with FETs 5 ₁ and8 ₁. In this case, the ground potential is supplied to one end and theother end of the first motor 1 ₁ and the ground potential is alsosupplied to one end and the other end of the second motor 1 ₂, therebythe drive current does not flow into the first motor 1 ₁ and the secondmotor 1 ₂ and enters the drive waiting condition.

Next, in the step S3, after elapse of an extremely short period fromstart of the step S2, the control unit 3 supplies, respectively as thecontrol voltages, the power supply voltage equal to that explained aboveto the gates of FETs 4 ₁, 4 ₂ of the FET switch pair 4, switches thesupply of the ground potential for the gates of FETs 5 ₁, 5 ₂ of the FETswitch pair 5 and also supplies the same power supply voltage as thatexplained above to the gates of FETs 8 ₁, 8 ₂ of the FET switch pair 8.With supply of these control voltages, FETs 4 ₂, 5 ₁, 8 ₂ turn ON, whileFETs 4 ₁, 5 ₂, 8 ₁ turn OFF. In this case, since the ground potential issupplied to the one end of first motor 1 ₁ via FET4 ₂ and the groundpotential is also supplied to the other end via FET8 ₂, a drive currentdoes not flow as illustrated in the time t1 to t2 of the upper currentwaveform of FIG. 2(b). Moreover, since the power supply voltage issupplied to one end of the second motor 1 ₂ via FET5 ₁ and the groundpotential is supplied to the other end via FET8 ₂, a drive current flowsas illustrated in the time t1 to t2 of the lower current waveform ofFIG. 2(b). Therefore, the second motor 1 ₂ rotates in one direction todisplace the position of the control object member coupled with thesecond motor 1 ₂.

In the subsequent step S4, after elapse of a constant period from startof the step S3, the control unit 3 supplies, respectively as the controlvoltages, the power supply voltage through the switching to the gates ofFETs 5 ₁, 5 ₂ of the FET switch pair 5 and also supplies the powersupply voltage equal to that explained above as the other controlvoltage. With supply of these control voltages, FET5 ₂ turns ON togetherwith FETs 4 ₂, 8 ₂ and FET5 ₁ is switched to turn OFF together with FETs4 ₁, 8 ₁. In this case, the ground potential is supplied to one end andthe other end of the first motor 1 ₁, the ground potential is alsosupplied to one end and the other end of the second motor 1 ₂ but adrive current does not flow into the first motor 1 ₁ and second motor 1₂ and enter the drive waiting condition.

Thereafter, in the step S5, after elapse of an extremely short period oftime from start of the step S4, the control unit 3 determines whether ornot the simultaneous drive command is issued to the first motor 1 ₁ andsecond motor 1 ₂. When it is determined (Y) that the simultaneous drivecommand to the first motor 1 ₁ and second motor 1 ₂ is issued, a seriesof this flowchart is completed and on the other hand, when it isdetermined (N) that the simultaneous drive command is not yet issued,the process returns to the first step S1 and the operations after thestep S1 are repeated.

As explained above, according to the flowchart of FIG. 2(a), the firstmotor 1 ₁ and second motor 1 ₂ can be driven simultaneously on the timedivision basis and thereby the control object member coupled with thefirst motor 1 ₁ and the control object member coupled with the secondmotor 1 ₂ can virtually be displaced in their positions simultaneously.

The flowchart explained above regards to an example where the firstmotor 1 ₁ and second motor 1 ₂ of the same set are driven simultaneouslyon the time division basis, but the third motor 1 ₃ and fourth motor 1 ₄of the same set can also be driven simultaneously on the time divisionbasis by supplying from the control unit 3 the control voltage of thesame polarity as that explained above to the FET switch pair 6 and FETswitch pair 7 of the second motor driving unit 2 ₂ as explained above inplace of the first motor driving unit 2 ₁.

Next, FIG. 3 is a circuit diagram illustrating a structure of theessential portion of the second embodiment of the motor drivingapparatus of the present invention. In this example, the positiondisplacement amount of the control object member with the first motor 1₁ is set equal to that of the control object member with the secondmotor 1 ₂.

As illustrated in FIG. 3, is also provided with a displacement amountdetecting unit 9 to respectively detect the position displacement amountof each control object member that is displaced with the first to fourthmotors 1 ₁ to 1 ₄, in addition to the structure of the motor drivingapparatus of the first embodiment and this displacement amount detectingunit 9 is connected to the control unit 1. Here, in FIG. 3, thestructural elements like those illustrated in FIG. 1 are designated withthe same reference numerals.

Moreover, FIG. 4 is a flowchart illustrating the operation process whenthe motors of the same set, for example, the first motor 1 ₁ and secondmotor 1 ₂ are driven simultaneously in the motor driving apparatus ofthe second embodiment.

Operations of the motor driving apparatus of the second embodiment willbe explained with reference to the flow chart of FIG. 3.

First, in the step S11, the control unit 3 detects the current positionof the first motor 1 ₁ through the displacement amount detecting unit 9and stores the detection result (drive start position) P₁₁ in theinternal memory.

Next, in the step S12, the control unit 3 drives the first motor 1 ₁ torotate under the same supply condition as that to the first motordriving unit 2 ₁ and third motor driving unit 2 ₃ in the step S1 of FIG.2 on the occasion of supplying the control voltage to the first motordriving unit 2 ₁ and third motor control unit 2 ₃ in order to set thesecond motor 1 ₂ to the rotation stop condition.

In this case, in the step S13, the control unit 3 measures the period inwhich the first motor 1 ₁ is driven to rotate.

Next, in the step S14, the control unit 3 determines whether or not therotation drive time of the first motor 1 ₁ has reached the preset time.When it is determined (Y) that the rotation drive time has reached thepreset time, the process goes to the next step S15. On the other hand,when it is determined (N) that the rotation drive time does not yetreach the preset time, the operations of the step S14 are repeated.

Subsequently, in the step S15, the control unit 3 stops the rotationdrive of the first motor 1 ₁ and also sets the second motor 1 ₂ to therotation drive condition explained above by setting the supply conditionthat is same as that of the control voltage to the first motor drivingunit 2 ₁ and the third motor driving unit 2 ₃ in the step S2 of FIG. 2,on the occasion of supplying the control voltage to the first motordriving unit 2 ₁ and third motor driving unit 2 ₃. In this case, in thestep S16, the control unit 3 detects the current position of the firstmotor 1 ₁ through the displacement amount detecting unit 9 and storesthe detection result (drive end position) P₁₂ in the internal memory.

In the subsequent step S17, the control unit 3 detects the currentposition of the second motor 1 ₂ via the displacement amount detectingunit 9 and then stores the detection result (drive start position) P₂₁in the internal memory.

Next, in the step S18, the control unit 3 drives the second motor 1 ₂ torotate to stop the rotation of the first motor 1 ₁ under the samecondition as that for supplying the control voltage to the first motordriving unit 2 ₁ and the third motor driving unit 2 ₃ in the step S3 ofFIG. 2 on the occasion of supplying the control voltage to the firstmotor driving unit 2 ₁ and third motor driving unit 2 ₃.

In this case, in the step S19, the control unit 3 measures the period todrive the second motor 1 ₂ to rotate.

Next, in the step S20, the control unit 3 determines whether therotation drive time of the second motor 1 ₂ has reached the preset timeor not. When it is determined (Y) that the rotation drive time hasreached the preset time, the operation goes to the next step S21 andwhen it is determined (N) that the rotation drive time does not yetreach the preset time, operations of this step S20 is repeated.

Here, as the preset times (rotation drive time) T₁ of the first motor 1₁ in the preceding step S14 and the present time (rotation drive time)T₂ of the second motor 1 ₂ in the step S20, the preset times T₁, T₂ thatare set in the preceding simultaneous drive are used, but since there isno preset time that is set in the preceding simultaneous drive when thefirst motor 1 ₁ and the second motor 1 ₂ are driven simultaneously, bothpreset times T₁, T₂ are set to the equal value. Subsequently, in thestep S21, the control unit 3 stops the rotation drive of the secondmotor 1 ₂ to also stop the rotation drive of the first motor 1 ₁ bysetting, at the time of supplying the control voltage to the first motordriving unit 2 ₁ and the third motor driving unit 2 ₃, the supplycondition that is same as that of the control voltage to the first motordriving unit 2 ₁ and the third motor driving unit 2 ₃ in the step S4 ofFIG. 2. In this case, in the step S22, the control unit 3 detects thecurrent position of the second motor 1 ₂ through the displacement amountdetecting unit 9 and stores the detection result (drive end position)P₂₂ in the internal memory. In the subsequent step S23, the control unit3 determines whether or not the simultaneous drive command to the firstmotor 1 ₁ and second motor 1 ₂ is completed as in the case of thedetermination in the step S5 of FIG. 2. When it is determined (Y) thatthe simultaneous drive command to the first motor 1 ₁ and second motor12 is completed, the processes in the flowchart come to the end, and onthe other hand, when it is determined (N) that the simultaneous drivecommand is not yet completed, the process goes to the next step S24.

Next, in the step S24, the control unit 3 calculates the coefficient K₁for setting the time duty to apply a drive current to the first motor ₁.This coefficient K1 ₁ is calculated based on the following formula (1)using the drive start position P₁₁ and drive end position P₁₂ of thefirst motor 1 ₁ and the drive start position P₂₁ and drive end positionP₂₂ of the second motor 1 ₂ stored in the internal memory.

K₁=|P₂₁−P₂₂|/(|P₁₁−P₁₂|+|P₂₁−P₂₂|)  (1)

Thereafter, in the step S25, the control unit 3 obtains the coefficientK₂ for setting the time duty to apply a drive current to the secondmotor 1 ₂. This coefficient K₂ can be calculated based on the followingformula (2) using the drive start position P₁₁ and drive end positionP₁₂ of the first motor 1 ₁and the drive start position P₂₁ and drive endposition P₂₂ of the second motor 1 ₂ stored in the internal memory.

K₂=|P₁₁−P₁₂|/(|P₁₁−P₁₂|+|P₂₁−P₂₂|)  (2)

Next, in the step S26, the control unit 3 calculates the next settingtimes (drive time ratios) T₁, T₂ using the drive basic time T_(B) fordriving simultaneously the first motor 1 ₁ and second motor 1 ₂ and thecalculated coefficients K₁, K₂. As the calculation formula, T₁=T_(B)×K₁is used for the setting time T₁ and T₂=T_(B)×K₂ is used for the settingtime T₂. When these setting times T₁, T₂ are calculated, the processreturns to the first step S11 and the operations of the step S11 andsubsequent steps are repeated.

Here, an example of the setting times T₁, T₂ in the second embodimentwill be explained. When it is assumed that the basic time T_(B) is 100msec, the drive start position P₁₁ of the first motor 1 ₁ is 50 and thedrive start position P₂₁ of the second motor 1 ₂ is also 50, if thedrive end position P₁₂ of the first motor 1 ₁ after elapse of the unittime becomes 100 and the drive end position P₂₂ of the second motor 1 ₂becomes 75, the drive displacement position |P₁₁−P₁₂| of the first motor1 ₁ becomes |100−50|=50 and the drive displacement position |P₂₁−P₂₂| ofthe second motor 1 ₂ becomes |100−75|=25. When K₁, K₂are obtained usingthe formulae (1), (2), K₁ becomes 25/(50+25)=⅓ and K₂ becomes50/(50+25)=⅔. As a result, the setting time T₁ becomes 100 msec×⅓=33.3msec, while the setting time T₂ becomes 100 msec×⅔=66.7 msec.

Namely, in this example, when the time duty to drive the first motor 1 ₁is set to 33.3 msec and the duty time to drive the second motor 1 ₂ isset to 66.7 msec for the total drive time of 100 msec, the drivedisplacement position |P₁₁−P₁₂| of the first motor 1 ₁ becomes equal tothe drive displacement position |P₂₁−P₂₂| of the second motor 1 ₂.

As explained above, according to an invention of the present invention,since two motors among a plurality of motors are formed as a set, oneend of the two motors forming a set is connected to the motor drivingunit common to a plurality of motors having one semiconductor switchpair and the other end is connected to the same motor driving unithaving two semiconductor switch pairs and thereby two motors are drivenon the time division basis via the two semiconductor switch pairs of thesame motor driving unit, there is provided the effect that the totalnumber of necessary motor driving units can be reduced in comparisonwith the total number of motors used, the total size of the motordriving unit can also be reduced and thereby low-cost motor driving unitcan be attained.

Moreover, according to the other invention of the present invention,since each drive time of two motors is adjusted to provide equalposition displacement amount of the control object member with twomotors forming a set, in addition to the effect attained by oneinvention of the present invention, there is provided the effect thatposition displacement amount of the control object member with twomotors driven simultaneously always becomes equal and thereby unbalancecondition when the control object member position is displaced can beeliminated.

What is claimed is:
 1. A motor driving apparatus comprising a pluralityof motors for displacing a position of a control object member duringrotation, a plurality of motor driving units having at least onesemiconductor switch pair to selectively connect the motors to a powersupply and a control unit for ON/OFF controlling the semiconductorswitch pair of the motor driving units, wherein a set of motors isformed of two motors, one end of the two motors forming the set isconnected to a common motor driving unit having one semiconductor switchpair and another end thereof is connected respectively to a motordriving unit having two semiconductor switch pairs and the control unitdrives, when the two motors forming the set are driven simultaneously,the two motors on a time division basis by ON/OFF controlling the twosemiconductor switch pairs to provide inverse output voltage polaritiesof the two semiconductor switch pairs of the motor driving unitconnected to the two motors.
 2. A motor driving apparatus comprising aplurality of motors for displacing a position of a control object memberduring rotation, a plurality of motor driving units having at least onesemiconductor switch pair to selectively connect the motors to a powersupply, a control unit for ON/OFF controlling the semiconductor switchpair and a displacement amount detecting unit for detecting a positiondisplacement amount of the control object member, wherein a set ofmotors is formed of two motors, one end of the two motors forming theset is connected to a common motor driving unit having one semiconductorswitch pair and another end thereof is respectively connected to a motordriving unit having two semiconductor switch pairs and the control unitdrives, when the two motors forming the set are driven simultaneously,the two motors on a time division basis by ON/OFF controlling the twosemiconductor switch pairs to provide inverse output voltage polaritiesof the two semiconductor switch pairs of the motor driving unitconnected to the two motors and also adjusts each drive time of the twomotors to provide an equal position displacement amount of the controlobject member with the two motors detected by the displacement amountdetecting unit.
 3. A motor driving apparatus according to claim 1,wherein the semiconductor switch pair is formed of a field effecttransistor pair connected in series across the power supply.
 4. A motordriving apparatus according to claim 2, wherein the semiconductor switchpair is formed of a field effect transistor pair connected in seriesacross the power supply.